This proposal is aimed at generating reagents with which to visualize the distribution of the transient receptor potential ion channel (TRPA1) protein in living animals. TRPA1 is expressed in sensory neurons of the trigeminal and dorsal root ganglia where it serves as the main sensor for environmental irritants or chemicals that cause tissue damage. It also plays a critical role in the development of hypersensitivity under inflammatory pain conditions, and is therefore considered an important target for the development of pain therapeutics. However, a major obstacle in further establishing the contribution of TRPA1 to cellular physiology, and in understanding how the channel is regulated under normal and inflammatory conditions, has been the lack of reagents with which to visualize the channel protein, either in fixed or in living tissue. Although several groups have reported the production of antibodies against TRPA1, these have generally exhibited low specificity or sensitivity. Moreover, antibodies can only be used in fixed tissues or in cell culture, precluding the study of the protein in intact living tissues. To address this shortcoming, we propose to generate novel genetic probes to visualize TRPA1 channels in fixed tissue and living cells. These probes, termed FingRs (fibronectin intrabodies generated with mRNA display), will be identified through a selection for proteins that bind TRPA1 from a library built on the highly stable fibronectin backbone. We anticipate that a TRPA1 FingR will be an extremely powerful tool, which could be used to examine the distribution of TRPA1 throughout the body, in a variety of cell types, in healthy and disease conditions. Moreover, the genetic nature of the material, wil allow it to be easily propagated and introduced into living cells.